STY: autopep8'ed test_authentication_plain

unittests/test_authentication_plain.py

@@ -34,8 +34,8 @@ from pytest import raises
 
 def test_subclass_configure():
     # TODO I do not see the meaning of this test.
-    #It only tests, that the call of the super version of configure sets the 
-    #password property. And that due to the subclassing no longer a password 
+    # It only tests, that the call of the super version of configure sets the
+    # password property. And that due to the subclassing no longer a password
     # argument can be provided.
     # Suggestion: Either remove this test or state in what context this test
     # is meanigful.